pyridylazo) - resorcinol (PAR) anionic chelate and the cations of some methoxybis(tetrazolium) salts (MT2+), which

contain different number of nitro groups {3,3'-(3,3'-dimethoxy-4,4'-biphenylene)bis[2,5-di(4-nitrophenyl)-2Htetrazolium] chloride (Tetranitrotetrazolium Blue chloride, TNBT), 3,3'-(3,3'-dimethoxy-4,4'-biphenylene)bis[2-(4-nitrophenyl)-5-phenyl-2H-tetrazolium] chloride (Nitro Blue Tetrazolium chloride, NBT) and 3,3'-(3,3'-dimethoxy-4,4'-biphenylene)-bis(2,5-diphenyl-2H-tetrazolium) chloride (Tetrazolium Blue chloride, BTC)} have been studied. The optimal conditions for extraction in chloroform (pH, concentrations of the reagents, extraction time) and the composition of the complexes (V:PAR:MT=2:4:3) have been found. The equilibrium constants (the constants of extraction – KEx, the constants of distribution – KD, the constants of formation – â), and the recovery factors have been determined. The results show that a linear relationship exists between LogKEx and the number of nitro groups included in MT2+ (NNO2): the higher NNO2, the lower LogKEx. A similar relationship has been established between Logâ and NNO2. These relationships have been used to predict the values of LogKEx and Logâ for new (uninvestigated) methoxybis(tetrazolium) ion-associated complexes.